TikZ diagrams for economists: A normal pdf with shaded area.

I have been dabbling with the TikZ package to create some diagrams relevant to a first year microeconomics course. The following diagram of the probability density function (pdf) of a normal distribution may be useful to others wishing to integrate similar diagrams into their LaTeX documents or Beamer presentations. To use, insert the following code anywhere you like within a .tex document (you must include \usepackage{tikz} in your header):